1. Field of the Invention
The present invention relates to a press apparatus for pressing a formed web. More particularly, the present invention relates to a press apparatus which includes an extended nip press.
2. Information Disclosure Statement
In the prior art, TRI-NIP or Tri-Vent presses followed by a fourth smoothing press have resulted in newsprint and fine paper having improved sheet symmetry. Such symmetry is achieved primarily by pressing one surface of the web directly against a press roll and then subsequently smoothing the opposite side of the web during movement of the web through the smoothing press, which is the fourth press in the aforementioned TRI-NIP configuration. TRI-NIP is a registered trademark of Beloit Corporation, and Tri-Vent is a common law mark of Beloit Corporation
The dryness of the web produced on the aforementioned machines is within the range 30 to 43 percent solids at 4,000 feet per minute.
Although an extended nip press is generally more expensive than a press including conventional roll couples, such is not necessarily the case when the cost of several spare rolls and ancillary equipment for the aforementioned TRI-NIP press is factored into costs. The cost of an extended nip press is, therefor, comparable and has the advantage that a sheet between 48 to 52 percent solids can be produced at 4,000 feet per minute.
More specifically, the TRI-NIP press or Tri-Vent press plus fourth press are relatively costly and are particularly labor intensive with regard to felt changes.
The present invention provides the following advantages. First, the number of press nips and press framework is reduced. Secondly, the clothing requirements, that is the number of press felts required, is reduced, thereby reducing the amount of time that the press is idle during felt changes.
Additionally, the dryness of the web out of the press is increased according to the configuration of the press apparatus according to the present invention.
The aforementioned objectives are attained in the present invention by providing an inverted single felted extended nip press in the first press position. Such ENP cooperates with a transfer felt so that the web will be riding on a bottom felt as it passes through a single felted roll press in the second press position. The second press only increases the dryness of the web by 2 to 3 percent but achieves the goal of generating a web that is less two-sided.
Therefore, it is a primary objective of the present invention to provide a press apparatus which increases the dryness of the resultant web while enhancing the resultant sheet symmetry.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.